Extraneous "unmet peer dependency" warning

[OliverJAsh]

Node 8.1.4, Yarn 1.1.0

Do you want to request a feature or report a bug?
Bug

What is the current behavior?

If the current behavior is a bug, please provide the steps to reproduce.

yarn add typescript
yarn add tslint
yarn add ix
yarn add tslib@^1.7.1

ix has a peer dependency of tslib@^1.7.1: https://github.com/ReactiveX/IxJS/blob/71277717f15bdf100218252326a2c95ea05d4b8a/package.json#L52

This peer dependency has been met, however, yarn warns that this has not been met:

❯ yarn add tslib@^1.7.1
yarn add v1.1.0
[1/4] 🔍  Resolving packages...
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
warning "ix@2.1.0" has unmet peer dependency "tslib@^1.7.1".
[4/4] 📃  Building fresh packages...
success Saved 0 new dependencies.
✨  Done in 0.98s.

I believe the issue only occurs when another dependency shares the peer dependency but as a normal dependency instead, as it the case with tslint, which depends on tslib@^1.7.1: https://github.com/palantir/tslint/blob/5ffec0910ff32e4b402859851822b1d1fe8eb3cf/package.json#L48

[leikind]

I think have a similar problem:

warning "url-loader@0.5.9" has unmet peer dependency "file-loader@*".

but I do have file-loader installed.

[BYK]

I think this will be fixed by #4613. I tried to reproduce this locally with the patch applied and wasn't able to.

[kaylie-alexa]

I can't repro either on latest master @OliverJAsh can you try one of the nightly builds? https://yarnpkg.com/en/docs/nightly

[bogdansoare]

also have a problem where a package says that it has unmet peer dependency , but the dependency is installed, I thought this was fixed in 1.2

[leikind]

A changelog would help users find out whether a certain bug is fixed or not, but there is no changelog.

[edmorley]

The issue as reported in the OP looks fixed to me in latest yarn (1.2.1), so this can be closed.

also have a problem where a package says that it has unmet peer dependency , but the dependency is installed, I thought this was fixed in 1.2

There are likely multiple causes, could you file a new issue with full STR? :-)
(See also #4675 which is peer dependency warnings from transitive dependencies)

[BYK]

Yeah, I've also verified that I cannot repro this on latest master (post 1.2.1) so closing.

[leikind]

if it is fixed, what am I doing wrong?

→ yarn install --check-files
yarn install v1.2.1
warning package.json: No license field
warning No license field
[1/5] 🔍  Validating package.json...
[2/5] 🔍  Resolving packages...
[3/5] 🚚  Fetching packages...
[4/5] 🔗  Linking dependencies...
warning "postcss-cssnext@3.0.2" has unmet peer dependency "caniuse-lite@^1.0.30000697".
warning "url-loader@0.5.9" has unmet peer dependency "file-loader@*".
warning "webpack-dev-server@2.9.1" has unmet peer dependency "webpack@^2.2.0 || ^3.0.0".
warning "webpack-dev-middleware@1.12.0" has unmet peer dependency "webpack@^1.0.0 || ^2.0.0 || ^3.0.0".
[5/5] 📃  Building fresh packages...
✨  Done in 16.53s.

→ grep 'file-loader' yarn.lock
    file-loader "^0.11.2"
file-loader@^0.11.2:
  resolved "https://registry.yarnpkg.com/file-loader/-/file-loader-0.11.2.tgz#4ff1df28af38719a6098093b88c82c71d1794a34"

file-loader is installed

[edmorley]

There are likely multiple causes, could you file a new issue with full STR? :-)

[phlegx]

I get the same warnings:

$ yarn install --check-files
yarn install v1.2.1
[1/4] Resolving packages...
[2/4] Fetching packages...
info fsevents@1.1.2: The platform "linux" is incompatible with this module.
info "fsevents@1.1.2" is an optional dependency and failed compatibility check. Excluding it from installation.
[3/4] Linking dependencies...
warning "postcss-cssnext@3.0.2" has unmet peer dependency "caniuse-lite@^1.0.30000697".
warning "vue-loader@13.3.0" has unmet peer dependency "css-loader@*".
warning "webpack-dev-server@2.9.4" has unmet peer dependency "webpack@^2.2.0 || ^3.0.0".
warning "webpack-dev-middleware@1.12.0" has unmet peer dependency "webpack@^1.0.0 || ^2.0.0 || ^3.0.0".
[4/4] Building fresh packages...
Done in 8.07s.

My package.json looks like this:

{
  "name": "example_app",
  "private": true,
  "dependencies": {
    "@rails/webpacker": "^3.0.2",
    "coffeescript": "^2.0.2",
    "vue": "^2.5.2",
    "vue-loader": "^13.3.0",
    "vue-template-compiler": "^2.5.2",
  },
  "devDependencies": {
    "webpack-dev-server": "^2.9.4"
  }
}

[growthcode]

@phlegx I was able to fix it after some guessing... I'm new to yarn but fixed 4 warnings including the one here.

[1/4] 🔍  Resolving packages...
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
warning "@rails/webpacker > postcss-cssnext@3.0.2" has unmet peer dependency "caniuse-lite@^1.0.30000697".
warning " > vue-loader@13.5.0" has unmet peer dependency "css-loader@*".
warning " > eslint-config-standard@10.2.1" has unmet peer dependency "eslint-plugin-standard@>=3.0.0".
warning " > webpack-dev-server@2.9.4" has unmet peer dependency "webpack@^2.2.0 || ^3.0.0".
warning "webpack-dev-server > webpack-dev-middleware@1.12.1" has unmet peer dependency "webpack@^1.0.0 || ^2.0.0 || ^3.0.0".
[4/4] 📃  Building fresh packages...
success Saved lockfile.
success Saved 1 new dependency.
└─ eslint-plugin-promise@3.6.0
✨  Done in 5.03s.

I'll list my fixes individually so you can see the pattern:

# 1) @rails/webpacker > postcss-cssnext@3.0.2" has unmet peer dependency "caniuse-lite@^1.0.30000697".
bin/yarn add caniuse-lite@^1.0.30000697

# 2) warning " > vue-loader@13.5.0" has unmet peer dependency "css-loader@*".
bin/yarn upgrade css-loader -p

# 3) warning " > webpack-dev-server@2.9.4" has unmet peer dependency "webpack@^2.2.0 || ^3.0.0".
# 4) warning "webpack-dev-server > webpack-dev-middleware@1.12.1" has unmet peer dependency "webpack@^1.0.0 || ^2.0.0 || ^3.0.0".
yarn upgrade webpack@^2.2.0 || ^3.0.0

Be sure to use the appropriate dependency flags referenced in the warning, more info here:
https://yarnpkg.com/lang/en/docs/managing-dependencies/

After I ran those lines... I got what I spent hours trying to achieve... 0 warnings 😄 :

⇒  yarn install --check-files
yarn install v1.3.2
[1/4] 🔍  Resolving packages...
[2/4] 🚚  Fetching packages...
[3/4] 🔗  Linking dependencies...
[4/4] 📃  Building fresh packages...
✨  Done in 7.45s.